This sounds like you’re trying to train a TensorFlow 2 model with the Keras Network Learner node, is that correct? Unfortunately, the Keras Network Learner node (and the entire KNIME Deep Learning - Keras Integration, for that matter) only supports TensorFlow 1. Currently, you’d need to resort to Python scripting via the DL Python Network Learner – KNIME Community Hub node if you wanted to train a TensorFlow 2 model.
Marcel